docChanges() does not include `removed` items

[wSedlacek]

First I would like to thank you Gustavo for all the hard work you have put into mocking Firebase.
I have been attempting to build out proper unit test when using Angular Fire and your mock of Firebase has been instrumental in building out proper mocks.

I am running into an issue with your mock of Firestore though. That is that it is only sending me the added docs but not removed or modified.

This is the section of code that I am getting stuck and and not getting past the short circuit.

mockbase/firestore/query-snapshot.ts

Lines 29 to 37 in e271ba2

	if (this === this.query.lastSnapshot || !this.query.lastSnapshot) {
	// Short circuit: this is the first snapshot, so all items were added.
	return this.docs.map((doc, newIndex) => ({
	type: "added",
	oldIndex: -1,
	newIndex,
	doc,
	}));
	}

This is where the lastSnapshot seems like it should be set to prevent that short circuit

mockbase/firestore/query.ts

Lines 41 to 55 in e271ba2

	public async emitChange() {
	if (!this.emitter.hasListeners(QUERY_SNAPSHOT_NEXT_EVENT)) {
	return;
	}
	// TODO: this emits even if there wasn't an actual change with the current filters
	const snapshot = await this.get();
	this.lastSnapshot = snapshot;
	this.emitter.emit(QUERY_SNAPSHOT_NEXT_EVENT, [snapshot]);
	}
	setNoInitialSnapshot(): this {
	this.noInitialSnapshot = true;
	return this;
	}

Code I am using

      const subject = new Subject();
      this.app
        .firestore()
        .collection(path)
        .onSnapshot({
          next: (collection) => {
            subject.next(
              collection.docChanges().map(({ type, doc }) => ({ type, payload: { doc } }))
            );
          },
          error: (err) => subject.error(err),
          complete: () => subject.complete(),
        });

      subject.subscribe(console.log);

I have played around with it for a bit but can't seem to figure out the exact cause. My guess is either (a) lastSnapshot isn't being set OR (b) the current snapshot and lastSnapshot are always in sync, or at least at the time when docChanges() runs from within a onSnapshot()

Again thank you so much for your work. Let me know if you need any more information or have any work arounds.

[gustavohenke]

Hey! I'm surprised to see someone else using this largely undocumented code 🙂
I'm glad that you've been able to find your way around the codebase.

The tests for QuerySnapshot are doing everything upside down:

mockbase/firestore/query-snapshot.test.ts

Lines 95 to 119 in e271ba2

	it("lists docs as modified when they have moved in the last snapshot", async () => {
	const docs = [
	new MockQueryDocumentSnapshot(query.firestore.doc("foo/bar"), {}),
	new MockQueryDocumentSnapshot(query.firestore.doc("foo/baz"), {}),
	];
	const snapshot1 = createSnapshot(docs);
	const snapshot2 = createSnapshot([docs[1], docs[0]]);
	query.lastSnapshot = snapshot2;
	const changes = snapshot1.docChanges();
	expect(changes).toHaveLength(2);
	expect(changes).toContainEqual({
	type: "modified",
	oldIndex: 0,
	newIndex: 1,
	doc: docs[0],
	});
	expect(changes).toContainEqual({
	type: "modified",
	oldIndex: 1,
	newIndex: 0,
	doc: docs[1],
	});
	});

I must have understood the docs as "since the last emitted snapshot" instead of "since the previous snapshot":

Returns an array of the documents changes since the last snapshot. If this is the first snapshot, all documents will be in the list as added changes.

Let's see if it's a fast fix.

[gustavohenke]

I've published v0.5.1 with a fix for this.
Let me know how it goes!

[wSedlacek]

Thank you for the quick reply! I have been testing v0.5.1 but I still don't seem to be getting the removed.

I have create a reproduction Code Sandbox.
https://codesandbox.io/s/clever-zhukovsky-o0h9v?file=/src/index.js

I expect to have console.log of Added Item which I get, followed by Modified Item which also works then I expect to have a console.log of Removed Item which I don't get.

[gustavohenke]

Coolio! v0.5.2 seems to have finally nailed it: https://codesandbox.io/s/vigilant-bas-fkpur?file=/src/index.js

Try it yourself and let me know how it goes.

[wSedlacek]

Fantastic! Thank you for all your hard work! We are getting much closer!
There was one more inconsistently I found with this latest patch.

If there are two items, and you delete the first one you get a modified rather then a removed

Example:
https://codesandbox.io/s/recursing-johnson-b6kl1?file=/src/index.js